Plants, like animals, get their start during embryogenesis. Plants,however, only pattern a basic body plan during embryogenesis, with their adult body forms bearing very little resemblance to the embryo. Given this diversity in postembryonic development, it is remarkable that plant embryos from a wide range of species go through very similar stages of development, many with stereotyped, almost invariant cell division patterns. It is therefore tempting for plant embryologists to explore the underlying molecular mechanisms of this patterning in many different types of plants. Adding to this temptation is the fact that genomic information for a multitude of experimentally tractable plants is now available at the click of a mouse. But how does one even begin to grow all of these plants, much less isolate their embryos? Editors María Suárez and Peter Bozhkov attempt to answer these questions by compiling protocols on Arabidopsis, maize, barley and spruce in the book Plant Embryogenesis. This collection of protocols covers the gambit of plant techniques, from general plant husbandry to laser-capture microscopy, and does so in a way that is both detailed and easy to follow.FIG1
Plant embryogenesis (Methods in Molecular Biology vol. 427) Edited by María F. Suárez and Peter V. Bozhkov Springer (2008) 184 pages ISBN 978-1-58829-931-4 £61.50 (hardback)
The book is divided into two parts, entitled Model Embryonic Systems and Cellular, Genetic and Molecular Mechanisms of Plant Embryogenesis. The first part introduces the reader to embryogenesis in Arabidopsis, maize and spruce. Chapter 1, by Soomin Park and John J. Harada, is a fairly comprehensive review of Arabidopsis embryogenesis that covers the patterning of the embryo from fertilization, discusses many known factors associated with specific embryonic stages/cell types, and touches on the roles and transport of the plant hormone auxin. Both the patterning of the apical/basal axis and the development of radial patterning are explored. A single figure depicts several developmental stages of Arabidopsisembryos, providing the reader with a reference for the descriptions in the text and protocols later in the book. After this smooth introduction, the next chapter on maize embryogenesis is a bit jarring. Instead of a review of the field, the chapter jumps right into protocols on growing maize in a greenhouse, generating immature embryo cultures, generating somatic embryos and performing in situ hybridizations. Although all of these protocols are well written and informative, the lack of a single depiction of maize embryogenesis and the paucity of references are a bit disappointing.
This book will probably not replace a good collaboration, [but] provides enough information to start thinking about working in a different species
The next chapter falls somewhere in between the first and the second in terms of content. This chapter, by Sara von Arnold and David Clapham, focuses on spruce somatic embryogenesis and includes a nice description of embryonic cell lines and some of the experiments that are now possible using them. These somatic embryos can be synchronized, allowing researchers to collect large amounts of tissue at any given stage. Pictures of somatic embryos and a model of embryonic development are included in the introduction, as well as a review of some of the genes expressed in these cultures. Protocols on generation,maintenance and transformation are interspersed with short descriptions of the effects of different hormones and of the behavior of the cultures.
The second section of the book is almost completely dedicated to a wide variety of different protocols. The protocols are in a standardized, helpful format, starting with a brief introduction that is followed by a materials and methods section. A notes section is also included to better explain certain steps in the protocols and to point out derivations and tips to the reader. This section begins with a guide by Erhard Kranz, Yoichiro Hoshino and Takashi Okamoto on how to generate embryos and extra-embryonic endosperm in maize using in vitro fertilization, and how to micromanipulate the resulting tissue. There are several figures depicting both the techniques and the apparatuses used, making a daunting set of protocols more approachable.
A different approach for studying the early stages of Arabidopsisembryogenesis is presented by Michael Sauer and Jirí Friml in the next chapter. Here, the authors describe how to isolate and culture embryos as they develop within the ovule, which limits the number of developmental aberrations often seen in somatic embryogenesis systems. This protocol allows for the treatment of these embryos with drugs or hormones, which is difficult (if not impossible) to perform when embryos develop in the silique (seed pod). A brief description of microscopic analysis, including morphology, visualization of fluorescent proteins and histochemical detection, is also included. A final approach to generating embryos in culture is provided by Simone de F. Maraschin, Sandra van Bergen, Marco Vennik and Mei Wang. Here, the generation of haploid, microspore-derived embryos from barley is well described and illustrated. This process has traditionally been used by breeders to derive homozygous barley lines, but can also be adapted to study embryogenesis in the laboratory.
The book then shifts gears from generating embryos to manipulating and analyzing them. Among the techniques discussed is how to transform Arabidopsis with Agrobacterium tumefaciens, and a very helpful table that describes multiple plant transformation vectors, along with a description of the different strains of Agrobacterium, can be found in these chapters. Robert Blanvillain and Patrick Gallois also provide a related discussion on promoter trapping using T-DNA transformation in Arabidopsis, together with a useful PCR-based method for cloning genomic DNA that flanks the T-DNA insertion sites which can be applied to the insertion lines discussed in the preceding chapters. In chapter 11, Michael Sauer and Jirí Friml describe the use of auxin-specific antibodies to determine the spatial accumulation of this hormone during embryogenesis. They also discuss the pros and cons of using this technique as opposed to auxin-responsive transgenes. In chapter 13, Andrei Smertenko and Patrick Hussey present a different immunolocalization protocol, with an emphasis on studying the plant cytoskeleton. The inclusion of both protocols is helpful as one is applied to Arabidopsis and the other to spruce.
The remaining three chapters are a bit more specialized in the techniques they describe, covering laser-capture microdissection techniques, protocols for tracking intercellular macromolecule trafficking in Arabidopsisembryos, and a combined TUNEL and immunolocalization protocol to detect programmed cell death and a protein of interest in the same embryo.
As a methods book, Plant Embryogenesis does a good job of presenting a variety of techniques in a very digestible format. The notes sections of each protocol are particularly useful and make the protocols much more informative. I believe it would have been beneficial to include a little more background on each of the model organisms discussed (with the exception of Arabidopsis), but those types of reviews can be found elsewhere. Students and post-docs new to the field are likely to find the detailed protocols helpful, and it will make a nice addition to the reference collection of school libraries or individual labs. Although this book will probably not replace a good collaboration with another laboratory, it provides enough information for researchers to at least start thinking about working in a different species.
